The aim of this proposal is to establish Drosophila as a model system for quantitative genetic dissection of complex neurotransmitter-modulated traits. The specific aims of this proposal are to: Use linkage disequilibrium mapping to screen for associations between SNPs in monoamine receptor and enzyme loci, and five phenotypes: prenupal heart rate, and the reflex behaviors grooming, grasping, quivering and self- Assess the repeatability of association studies suing sibship-based statistical designs. Characterize the mutational distribution due to single P-element transposable element insertions affecting tyrosine- and dopa- decarboxylase activity, and identify up to 10 insertions that demonstrably affect genes involved in these traits.